CN111735769B - Traffic sign retroreflection coefficient rapid measurement device and method - Google Patents
Traffic sign retroreflection coefficient rapid measurement device and method Download PDFInfo
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- CN111735769B CN111735769B CN202010785873.3A CN202010785873A CN111735769B CN 111735769 B CN111735769 B CN 111735769B CN 202010785873 A CN202010785873 A CN 202010785873A CN 111735769 B CN111735769 B CN 111735769B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/55—Specular reflectivity
- G01N21/552—Attenuated total reflection
Abstract
The application discloses a traffic sign retroreflection coefficient rapid measurement device and a method, wherein the device comprises a laser, a transmitting unit, a receiving unit, a photoelectric detector and a control unit; the first receiving unit receives an echo signal formed by a retro-reflective target reflecting the laser pulse signal at a first observation angle to acquire first point cloud data; the second receiving unit receives echo signals formed by the retro-reflective target reflecting the laser pulse signals at a second observation angle different from the first observation angle, second point cloud data is obtained, and the control unit determines the retro-reflective coefficient of the retro-reflective target according to the incident angle, the incident light intensity, the first observation angle, the first point cloud data, the second observation angle and the second point cloud data. Compared with the prior art, the retroreflection coefficient measuring technology is less affected by environmental illumination and has high measuring precision.
Description
Technical Field
The application relates to the technical field of material analysis or test by using an optical means, in particular to a device and a method for quickly measuring the retroreflection coefficient of retroreflection materials such as traffic signs.
Background
The retroreflective material (broadly called retroreflective material) is widely applied to the fields of road traffic signs, marked lines, delineators, vehicle reflective signs, motor vehicle license plates, special operation clothing, fire indications, railway signs, industrial and mining safety production signs and the like, and plays an important role in the aspects of traffic safety, safety production and the like.
The coefficient of retroreflection, or retroreflectance, commonly known as reflected brightness, in candelas per lux per square meter, is an important indicator for determining the performance of retroreflective materials. It is known to measure the coefficient of retroreflection using active imaging. However, the emitted light projected on the retroreflector by the active light source is strong, and the dynamic range of the camera is limited, so that the quantization error is large, and the measurement result is inaccurate. In addition, there is a method of measuring the retroreflection coefficient of the traffic sign by combining the laser radar and the camera, but this method is greatly affected by the ambient light, and the influence of the incident angle and the observation angle of the retroreflection coefficient on the measurement result is not usually considered, resulting in low measurement accuracy.
For example, patent document 1 discloses that a retroreflection coefficient corresponding to each detection is determined based on a preset relationship between laser reflection intensity information and retroreflection coefficient and point cloud data. However, the method does not consider the intensity of the emitted laser, and simply corresponds the retroreflection coefficient with the laser reflection intensity information, so that the retroreflection coefficient measurement value has low reliability and poor accuracy. Meanwhile, the detector is easily influenced by other light sources in the environment and is influenced by the initial responsivity of the photoelectric detector, and the measurement precision is limited to a great extent.
Patent document 2 discloses a device for measuring the photometric property of a road marking, which is a measuring device for measuring the absolute value of the retroreflection coefficient, and the retroreflection coefficient is measured at only one observation angle in a fixed laser beam direction, and is also susceptible to interference from other light sources in the environment, resulting in low measurement accuracy. Meanwhile, the device needs to be calibrated before each measurement, and during the measurement, laser spots need to be ensured to be aligned to a single road marking, and a plurality of road markings exist in the same view field, which also causes the problem of low measurement efficiency.
Patent document 1: CN 110441269A;
patent document 2: CN 210198958U.
Disclosure of Invention
The application aims to provide a device and a method for quickly measuring the retroreflection coefficient of retroreflection materials such as traffic signs and the like so as to improve the accuracy of measurement results.
According to a first aspect of the application, a traffic sign coefficient of retroreflection measuring device comprises:
a laser for generating a laser pulse signal;
the transmitting unit is connected with the laser and is used for transmitting the laser pulse signal with preset incident light intensity to a retro-reflective target at a certain incident angle;
the receiving unit is used for receiving an echo signal formed by reflecting the laser pulse signal by a retro-reflective target;
the photoelectric detector is connected with the receiving unit and used for generating point cloud data according to the echo signals, and the point cloud data comprises detection point data of the retro-reflective target and reflection light intensities respectively corresponding to the detection points; and
the control unit is connected with the laser and the photoelectric detector;
the receiving unit comprises a first receiving unit and a second receiving unit, the photoelectric detector comprises a first photoelectric detector and a second photoelectric detector, the first photoelectric detector is connected with the first receiving unit, and the second photoelectric detector is connected with the second receiving unit;
the first receiving unit receives an echo signal formed by a retro-reflective target reflecting the laser pulse signal at a first observation angle, and first point cloud data is acquired; the second receiving unit receives an echo signal formed by the retro-reflective target reflecting the laser pulse signal at a second observation angle different from the first observation angle, and second point cloud data is obtained;
and the control unit determines a retroreflection coefficient of a retroreflection target according to the incident angle, the incident light intensity, the first observation angle, the first point cloud data, the second observation angle and the second point cloud data.
According to a further embodiment of the first aspect, the apparatus further comprises: and the image acquisition unit is used for acquiring the image data of the retro-reflective target, which contains color information.
According to another embodiment of the first aspect, the laser further comprises an optical fiber scanning unit and an optical fiber array, the optical fiber scanning unit and the optical fiber array are arranged between the laser and the emitting unit, and the optical fiber scanning unit is connected with the control unit.
According to another embodiment of the first aspect, the optical fiber scanning device further comprises an optical fiber scanning unit and an optical fiber array, the optical fiber scanning unit and the optical fiber array are arranged between the receiving unit and the photodetector, and the optical fiber scanning unit is connected with the control unit.
According to a second aspect of the present application, a method of measuring a coefficient of retroreflection of a traffic sign, the method comprising:
emitting a laser pulse signal with a predetermined incident light intensity to the retro-reflective target at a predetermined incident angle;
receiving an echo signal formed by a retro-reflective target reflecting the laser pulse signal at a first observation angle, and acquiring first point cloud data, wherein the first point cloud data comprises first reflected light intensity information;
receiving an echo signal formed by the retro-reflective target reflecting the laser pulse signal at a second observation angle different from the first observation angle, and acquiring second point cloud data, wherein the second point cloud data comprises second reflected light intensity information; and
and determining the retroreflection coefficient of the retroreflection target according to the incident angle, the incident light intensity, the first observation angle, the first reflected light intensity, the second observation angle and the second reflected light intensity.
According to a further embodiment of the second aspect, the angle of incidence, the first observation angle and the second observation angle are determined by the position of the transmitting unit of the laser pulse signal, the first receiving unit receiving the echo signal and the second receiving unit relative to the retro-reflective target.
According to a further embodiment of the second aspect, further comprising acquiring an image comprising color information of the retro-reflective target.
Further, the method also comprises the step of segmenting a color area of the image, and corresponding the color area to the corresponding positions of the first point cloud data and the second point cloud data.
According to a further embodiment of the second aspect, the method further comprises calculating a difference between the retroreflection systems measured at the first and second observation angles, and comparing the difference with a threshold value to determine the retroreflection coefficient.
Further, the threshold value is a difference value between minimum normal retroreflection coefficients of the retroreflection target corresponding to the first observation angle and the second observation angle under the incident angle condition.
Further, the difference between the first observation angle and the second observation angle is less than 1 degree
Based on the above-mentioned technical scheme that this application provided, compare with prior art, this contrary reflectance measurement technique is influenced by ambient illumination for a short time, and measurement accuracy is high.
Further features of the present application and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which is to be read in connection with the accompanying drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
FIG. 1 is an exemplary scenario of an application of a retro-reflection coefficient measuring apparatus;
FIG. 2 is a schematic view of a device for measuring coefficient of retroreflection according to a first embodiment of the present application;
FIG. 3 is a schematic diagram of a method for measuring coefficient of retroreflection;
FIG. 4 is a schematic diagram of a laser emitting system according to another embodiment of the present application;
FIG. 5 is a schematic diagram of a laser receiver system according to another embodiment of the present application;
FIG. 6 is a schematic diagram of another laser receiver system according to another embodiment of the present application;
FIG. 7 is a schematic flow chart of a method for measuring a coefficient of retroreflection according to an embodiment of the present disclosure.
In the figure:
10-measuring device:
11-laser, 12-emission unit, 13-emission fiber scanning unit, 14-emission fiber array;
21-a first receiving unit, 22-a first photodetector, 23-a first receiving fiber scanning unit, 24-a first receiving fiber array;
31-a second receiving unit, 32-a second photodetector, 33-a second receiving fiber scanning unit, 34-a second receiving fiber array;
40-an image acquisition unit;
50-a control unit;
20-a carrier;
100-retroreflector, 101-roadside traffic sign, 102-pavement traffic sign.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the application, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. Moreover, when a statement such as "at least one of" appears after a list of listed features, the entirety of the listed features is modified rather than modifying individual elements in the list. Furthermore, when describing embodiments of the present application, the use of "may" mean one or more embodiments of the present application. Also, the term "exemplary" is intended to refer to an example or illustration.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
Fig. 1 shows an exemplary scenario for an application of the retroreflection coefficient measuring apparatus 10. As shown in fig. 1, the measuring device 10 is mounted on a vehicle 20, for example, on the roof of the vehicle 20. When the vehicle 20 travels on a road, the measuring device 10 measures the retroreflection coefficient of a roadside traffic sign 101 (such as a speed limit traffic sign, a directional traffic sign, etc.) arranged on the side of the road or a road traffic sign 102 (such as a lane marking, an indication arrow, etc.) arranged on the road surface to determine whether the retroreflection performance of the sign meets the normal use requirement.
Although fig. 1 illustrates an onboard platform version of the measuring device 10, the present application is not limited to the platform version, and various mobile platforms, such as an unmanned airborne platform, are equally applicable. Meanwhile, the device 10 for measuring the retroreflection coefficient disclosed by the present application is not limited to measuring the retroreflection coefficient of the road traffic sign, but is applicable to measuring the retroreflection coefficient of any retroreflective material product, such as wearable signs, warning signs, and the like, such as clothing signs, helmet signs, and the like.
Furthermore, the measuring device 10 may be installed on a platform in a fixed area such as a laboratory or an inspection shop, so that the retro-reflection coefficient measurement of a target placed in front may be performed without moving.
Referring to fig. 2, a retroreflection coefficient measuring apparatus 10 according to an embodiment of the present application includes an optical transmission system, an optical reception system, and a control unit.
The optical transmission system includes a laser 11 for generating a laser pulse signal; a transmitting unit 12 connected to the laser 11 for transmitting the laser pulse signal with a predetermined incident light intensity to the retro-reflector 100 at a certain incident angle.
The optical receiving system comprises a receiving unit, a receiving unit and a control unit, wherein the receiving unit is used for receiving an echo signal formed by reflecting the laser pulse signal by a retro-reflective target; and the photoelectric detector is connected with the receiving unit and used for generating point cloud data according to the echo signals, and the point cloud data comprises detection point data of the retro-reflective target and reflection light intensities respectively corresponding to the detection points.
The transmitting unit 12 and the receiving unit may for example each comprise a set of optical lens devices, as will be appreciated by the skilled person.
According to an embodiment of the present application, the receiving unit includes a first receiving unit 21 and a second receiving unit 31, the photodetector includes a first photodetector 22 and a second photodetector 32, the first photodetector 22 is connected with the first receiving unit 21, and the second photodetector 32 is connected with the second receiving unit 31.
The first receiving unit 21 receives an echo signal formed by reflecting the laser pulse signal by a retro-reflective target at a first observation angle, and acquires first point cloud data through the first photodetector 22; the second receiving unit receives an echo signal formed by the laser pulse signal reflected by the retro-reflective target at a second observation angle different from the first observation angle, and acquires second point cloud data through a second photoelectric detector 32.
Referring to fig. 3, the transmitting unit 12, the first receiving unit 21, and the second receiving unit 31 are disposed in the measuring apparatus 10 in a certain relative positional relationship. After the laser 11 is started to work and scan the retroreflective object 100, a laser pulse signal is incident on the surface of the retroreflective object 100 via the transmitting unit 12 at a certain incident angle, where the retroreflective object 100 may be, for example, a roadside traffic sign 101 or a road traffic sign 102. Here, the incident angle is an angle α between the incident laser pulse signal and the normal vector of the mark.
In fig. 3, the laser echoes reflected by the roadside traffic sign 101 or the road traffic sign 102 enter the first receiving unit 21 and the second receiving unit 31, respectively. The first observation angle, that is, the observation angle of the first receiving unit 21, is an included angle between the incident direction of the incident laser pulse signal and a connection line between an incident point of the incident laser pulse signal on the roadside traffic sign 101 or the road traffic sign 102 and the first receiving unit 21β 1. Similarly, the second observation angle, that is, the observation angle of the second receiving unit 31 is an included angle between the incident direction of the incident laser pulse signal and a connecting line between the incident point of the incident laser pulse signal on the roadside traffic sign 101 or the road traffic sign 102 and the second receiving unit 31β 2。
In the embodiment shown in FIG. 3, the second observation angleβ 2Greater than a first observation angleβ 1However, as will be understood by those skilled in the art, the second observation angle is set in the measuring apparatus 10 in different relative positional relationships with respect to the retro-reflector 100 according to the transmitting unit 12, the first receiving unit 21, and the second receiving unit 31β 2First observation angleβ 1And a second observation angleβ 2The size relationship between the two is changed correspondingly, so the size relationship between the two is not limited by the application, but the two are required to be ensured to be different.
The laser echo passes through the first receiving unit 21 and the second receiving unit 31, and acts on the photosensitive surfaces (focal surfaces) of the corresponding first photodetector 22 and the second photodetector 32, respectively, so as to be converted into an electric pulse signal.
Referring to fig. 4, according to another embodiment of the present application, a transmitting fiber scanning unit 13 and a transmitting fiber array 14 are further connected between the laser 11 and the transmitting unit 12 in sequence.
The emission fiber scanning unit 13 is configured to sequentially couple the laser pulse signals emitted by the laser 11 into corresponding fibers in the emission fiber array 14.
The emission fiber scanning unit 13 may drive optical elements such as an optical fiber, a prism, or a mirror with an electromagnet or a stepping motor to realize optical path switching, or realize modulation of refractive index with a thermo-optical effect of a waveguide material, and change the refractive index of the material by a change of an electric field with a Pockels effect or a Franz-Keldysh effect of the material, for example.
The emitting fiber array 14 is disposed on the fiber panel to form a uniformly arranged ring shape, such as a circle, and a central fiber of the ring fiber array is connected to the laser 11.
The control unit is connected with the laser 11 and the emission optical fiber scanning unit 13, and is used for controlling the switching action of the emission optical fiber scanning unit 13 to be synchronous with the emission of the laser pulse signal of the laser 11.
Referring to fig. 5 and 6, according to another embodiment of the present disclosure, the first receiving fiber array 24 and the first receiving fiber scanning unit 23 are sequentially connected between the first receiving unit 21 and the first photodetector 22, and the second receiving fiber array 34 and the second receiving fiber scanning unit 33 are sequentially connected between the second receiving unit 31 and the second photodetector 32.
The first receiving fiber array 24 is coupled to the first receiving unit 21, and is configured to receive the laser echo acquired by the first receiving unit 21. The second receiving fiber array 34 is coupled to the second receiving unit 31 for receiving the laser echo acquired by the second receiving unit 31.
Optionally, the first receiving fiber array 24 and the second receiving fiber array 34 have the same composition structure as the transmitting fiber array 14, that is, the first receiving fiber array 24 and the second receiving fiber array 34 are disposed on a fiber panel to form a uniformly arranged ring shape, such as a circle, a center position of the ring fiber array, such as a circle center position, and a center fiber is connected to the corresponding first photodetector 22 and the corresponding second photodetector 32.
The first receiving fiber scanning unit 23 and the second receiving fiber scanning unit 33 are respectively connected to the control unit 50, the first receiving fiber scanning unit 23 is configured to sequentially scan the laser echoes received by the fibers of the first receiving fiber array 24 onto the photosensitive surface (focal surface) of the first photodetector 22 according to a control signal of the control unit 50, and the second receiving fiber scanning unit 33 is configured to sequentially scan the laser echoes received by the fibers of the second receiving fiber array 34 onto the photosensitive surface (focal surface) of the second photodetector 32 according to the control signal of the control unit 50.
Alternatively, the first receiving fiber scanning unit 23 and the second receiving fiber scanning unit 33 have the same composition structure as the emitting fiber scanning unit 13, and for example, the optical path switching may be realized by driving optical elements such as a fiber, a prism, or a mirror with an electromagnet or a stepping motor, or the modulation of the refractive index may be realized by using the thermo-optical effect of the waveguide material, and the refractive index of the material may be changed by changing the electric field by using the Pockels effect or the Franz-Keldysh effect of the material.
The control unit 50 performs laser scanning of the retroreflective article 100 by operating in synchronization with a predetermined timing in the transmitting signal path and the receiving signal path.
The coefficient of retroreflection is known to be related to the color of the retroreflector. In order to be able to accurately measure the retroreflection coefficient of different colored counter reflectors 100, for example, the traffic sign may be white, red, green, etc. according to different functions, according to another embodiment of the present application, the measuring device 10 further comprises an image acquisition unit 40 for acquiring image data of the counter reflector 100 containing color information. The image acquisition unit 40 may be, for example, a CCD module.
In the present application, the measurement device 10 further comprises a navigation positioning system, optionally, the navigation positioning system comprises an antenna, an Inertial Measurement Unit (IMU) and/or a satellite positioning module, such as beidou, GPS, GLONASS, GALILEO, etc. Alternatively, the measuring device 10 can be in data communication with a navigational positioning system of the onboard or airborne platform to obtain positioning information. Still alternatively, the testing device is provided with a wireless communication unit which acquires the positioning information from, for example, a server side by using a communication method such as bluetooth, wifi, or GPRS.
According to another embodiment of the present application, there is also disclosed a method of measuring a retroreflection coefficient, as shown in fig. 7, the method including the steps of:
referring to fig. 3, the laser pulse signal emitting unit 12 emits a laser pulse signal having a predetermined light intensity toward a retro-reflective target, such as a roadside traffic sign 101, at a predetermined incident angle α. Here, the incident angle is an angle α between the incident laser pulse signal and the normal vector of the mark, that is:
wherein the content of the first and second substances,
which is the direction in which the laser light is incident,
the normal vector of the plane is identified for traffic.
102, receiving an echo signal formed by a retro-reflective target reflecting the laser pulse signal at a first observation angle, and acquiring first point cloud data, wherein the first point cloud data comprises first reflected light intensity information;
with continued reference to fig. 3, the first receiving unit 21 is at a first observation angleβ 1Receiving an echo signal formed by reflecting the laser pulse signal by the roadside traffic sign 101, and acquiring a first point according to the echo signal by using a photoelectric detectorCloud data, the first point cloud data containing first reflected light intensity information.
103, receiving an echo signal formed by the retro-reflective target reflecting the laser pulse signal at a second observation angle different from the first observation angle, and acquiring second point cloud data, wherein the second point cloud data comprises second reflected light intensity information;
referring also to fig. 3, the first receiving unit 31 is at a second observation angleβ 2And receiving an echo signal formed by the road side traffic sign 101 reflecting the laser pulse signal, and acquiring second point cloud data by using a photoelectric detector according to the echo signal, wherein the second point cloud data comprises second reflected light intensity information.
The incident angle, the first observation angle, and the second observation angle are determined by the positions of the transmitting unit 12 of the laser pulse signal, the first receiving unit 21 that receives the echo signal, and the second receiving unit 31 with respect to the roadside traffic sign 101. Alternatively, the relative positions of the transmitting unit 12, the first receiving unit 21 and the second receiving unit 31 on the measuring device are fixed, and the angle is set by adjusting the relative position with the retro-reflective target. Alternatively, the relative positions of the transmitting unit 12, the first receiving unit 21 and the second receiving unit 31 on the measuring device can be adjusted, and the angle setting can be realized by accurately adjusting the relative positions of the units. Or the relative position between the units and the relative position of the retro-reflection target can be adjusted to realize the angle setting, so that the angle setting range is expanded, and the application range of the measuring device is expanded.
If the difference between the laser echo signals received by the first observation angle and the second observation angle is too large, the consistency of the quantization precision of the first detector and the second detector in the interval is influenced. In the application, the first observation angle can receive the laser echo, and the second observation angle can also receive the laser echo signal as far as possible, so that the measurement precision is improved. Therefore, in the present application, the difference between the first observation angle and the second observation angle is less than 1 °.
In addition, those skilled in the art will understand that the steps 102 and 103 are not executed in the exact order described above, and in fact, the step 103 may be executed first, the step 102 is executed, or the steps 102 and 103 are executed simultaneously.
And 104, determining a retroreflection coefficient of the retroreflection target according to the incident angle, the incident light intensity, the first observation angle, the first reflected light intensity, the second observation angle and the second reflected light intensity.
Coefficient of retroreflection strengthR EAnd coefficient of retroreflectionR APositive correlation, coefficient of retroreflection strengthR EDefined as the intensity of laser echo light received by the photodetectorI rWith the intensity of the emitted laser pulseI eThe ratio of (A) to (B) is as follows:
wherein the coefficientsa、bCalibration can be performed experimentally. Wherein the coefficientsaThe value of (A) is related to the response sensitivity or gain of the photodetector, coefficientbThe value of (c) is related to the initial responsivity of the photodetector, the ambient light level.
Thus, at the incident angle α, the first observation angleβ 1Measured coefficient of retroreflectionR A1Comprises the following steps:
at an incident angle alpha, a second observation angleβ 2Measured coefficient of retroreflectionR A2Comprises the following steps:
in the above formula, the first and second carbon atoms are,I 1、I 2respectively, the incident angle is alpha, and the observation angle is respectivelyβ 1、β 2And the intensity of the received laser echo light.
Because the received laser echo light intensity is greatly influenced by the environment, the measurement error is large under different environments. In order to solve the problem, the laser echo is received at the same incident angle and different observation angles, and the difference value between the retroreflection coefficients measured at different observation angles is calculated, namely:
suppose thatβ 1 < β 2As can be seen from the above formula, the initial responsivity and the ambient light illumination, i.e., the coefficient, of the photodetector are eliminatedbInfluence on determining retroreflection coefficientI = I 1- I 2Only the observation angle is concerned, thereby improving the measurement precision.
According to another embodiment of the application, the method further includes acquiring a color image of the reverse reflector, wherein the color image includes color information, segmenting different color regions by using an image processing technology, and respectively corresponding the color regions to corresponding positions of the first point cloud data and the second point cloud data, so as to obtain the retroreflection coefficient difference value corresponding to the color regions.
In the present application, the control unit 50 may detect the position of the retro-reflective mark according to the color image obtained by the CCD module, compare the retro-reflective mark with the standard traffic mark shape, and calculate the normal vector of the retro-reflective mark according to the curvature or inclination degree
。
In addition, the control unit 50 divides the retro-reflective mark into retro-reflective areas with different colors, and then determines the incident angle alpha and the first observation angle of the laser to the retro-reflective mark according to the relative positions of the receiving and transmitting unit and the receiving unitsβ 1And a second observation angleβ 2。
Table 1 below shows an example of minimum inverse emission coefficients corresponding to various colors under different observation angles and incident angles. For example, at an observation angle of 0.2 ° and an incidence angle of 15 °, the minimum retroreflection coefficient of the red mark should be 14 candelas per lux per square meter, below which the retroreflection performance of the mark is not satisfactory for use.
TABLE 1 minimum retroreflection coefficient for each color under different observation angles and incidence angles
The retroreflection refers to that a reflection light path is transmitted along an original incident light path, reflected light is concentrated in a small solid angle, according to the law of conservation of energy, the reflected light intensity at a small observation angle is strong, and the luminous intensity at a large observation angle is weak, so that the larger the difference between the reflected light intensity and the luminous intensity, the better the retroreflection performance is. On the contrary, the difference between the light intensities of the two observation angles is small or no difference, which may be caused by the diffuse reflection of the incident light by the retro-reflector, i.e. the retro-reflection performance is poor. Therefore, the method compares the calculated retroreflection coefficient difference value with a threshold value, and then judges whether the retroreflection coefficient of the mark meets the requirement. Preferably, the threshold value is a difference between minimum retroreflection coefficients of the retroreflector corresponding to the first observation angle and the second observation angle under the incident angle condition, and the minimum retroreflection coefficient refers to a retroreflection coefficient of the retroreflector which meets the retroreflection performance requirement (i.e., is qualified) under the predetermined incident angle and observation angle condition.
For example, as can be seen from the above table, the retroreflective article made of a white-class I material has a minimum coefficient of retroreflection of 50 cd · lx at an entrance angle of 15 ° and an observation angle of 0.2 °-1·m-2The minimum retroreflection coefficient at an observation angle of 0.5 DEG is 23 cd · lx-1·m-2Then, for the retroreflector to satisfy the performance requirement, the normal retroreflectivity difference corresponding to the two observation angles should be at least 27 cd · lx-1·m-2. Therefore, if the measuring device of the present application measures the difference in the retroreflectivityR A1- R A227 cd · lx or more (not less)-1·m-2And judging that the retroreflection coefficient of the retroreflection mark meets the use requirement.
The threshold value can be determined according to the above table, but those skilled in the art should understand that the values and the value intervals listed in the above table are only exemplary and are only used for explaining the technical idea of the present application, and the values or options in the above table, such as the observation angle, the incident angle, the color, etc., can be arbitrarily and reasonably set in practical application.
The application takes the retroreflection coefficient difference value obtained through two observation angles as a judgment basis, and judges whether the retroreflection performance of the retroreflection body meets the requirement or not, so that the influence of environmental illumination on retroreflection coefficient measurement is eliminated, and the measurement precision is high.
In addition, because the retro-reflector is sensitive to the observation angle abnormity, the two observation angles are measured simultaneously, the obtained measurement result is richer, and the measurement result is more accurate.
In addition, this application adopts optic fibre scanning system and fiber array, and each module spatial layout of device is convenient, scanning point evenly distributed in the visual field to scanning speed is fast, can produce more horizontal scanning points on the sign, and then is favorable to measuring reliable and stable contrary reflectance.
The above embodiments are only for illustrating the technical solutions of the present application and not for limiting the same, and although the present application is described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: modifications to the embodiments of the present application or equivalent replacements of some technical features may be made without departing from the spirit of the technical solution of the present application, which is to be covered by the technical solution of the present application.
Claims (9)
1. A traffic sign coefficient of retroreflection measuring device comprising:
a laser for generating a laser pulse signal;
the transmitting unit is connected with the laser and is used for transmitting the laser pulse signal with preset incident light intensity to a retro-reflective target at a certain incident angle;
the receiving unit is used for receiving an echo signal formed by reflecting the laser pulse signal by a retro-reflective target;
the photoelectric detector is connected with the receiving unit and used for generating point cloud data according to the echo signals, and the point cloud data comprises detection point data of the retro-reflective target and reflection light intensities respectively corresponding to the detection points; and
the control unit is connected with the laser and the photoelectric detector;
the receiving unit is characterized by comprising a first receiving unit and a second receiving unit, the photoelectric detector comprises a first photoelectric detector and a second photoelectric detector, the first photoelectric detector is connected with the first receiving unit, and the second photoelectric detector is connected with the second receiving unit;
the first receiving unit receives an echo signal formed by a retro-reflective target reflecting the laser pulse signal at a first observation angle, and first point cloud data is acquired; the second receiving unit receives an echo signal formed by the retro-reflective target reflecting the laser pulse signal at a second observation angle different from the first observation angle, and second point cloud data is obtained;
the control unit determines a retroreflection coefficient of a retroreflection target according to the incident angle, the incident light intensity, the first observation angle, the first point cloud data, the second observation angle and the second point cloud data;
the control unit calculates a difference value between the retroreflection coefficients measured by the first observation angle and the second observation angle, and compares the difference value with a threshold value to judge whether the retroreflection coefficient of the retroreflection target meets the requirement.
2. The traffic sign coefficient of retroreflection measurement device of claim 1, further comprising: and the image acquisition unit is used for acquiring the image data of the retro-reflective target, which contains color information.
3. The device for measuring the retroreflection coefficient of a traffic sign according to claim 1, further comprising an optical fiber scanning unit and an optical fiber array disposed between the laser and the emitting unit, wherein the optical fiber scanning unit is connected to the control unit.
4. The device of claim 1, further comprising a fiber scanning unit and a fiber array disposed between the receiving unit and the photodetector, wherein the fiber scanning unit is connected to the control unit.
5. A method for measuring the coefficient of retroreflection of a traffic sign, the method comprising:
emitting a laser pulse signal with a predetermined incident light intensity to the retro-reflective target at a predetermined incident angle;
receiving an echo signal formed by a retro-reflective target reflecting the laser pulse signal at a first observation angle, and acquiring first point cloud data, wherein the first point cloud data comprises first reflected light intensity information;
receiving an echo signal formed by the retro-reflective target reflecting the laser pulse signal at a second observation angle different from the first observation angle, and acquiring second point cloud data, wherein the second point cloud data comprises second reflected light intensity information; and
determining a retroreflection coefficient of a retroreflection target according to the incident angle, the incident light intensity, the first observation angle, the first reflected light intensity, the second observation angle and the second reflected light intensity;
and calculating a difference value between the retroreflection coefficients measured by the first observation angle and the second observation angle, and comparing the size relation between the difference value and a threshold value to judge whether the retroreflection coefficient of the retroreflection target meets the requirement.
6. The method of claim 5, wherein the incident angle, the first observation angle, and the second observation angle are determined by a position of the transmitting unit of the laser pulse signal, the first receiving unit of the echo signal, and the second receiving unit relative to the retro-reflective target.
7. The method of claim 5, further comprising obtaining an image containing color information of the retroreflective target.
8. The method of claim 7, further comprising segmenting a color region of the image and corresponding the color region to a corresponding location of the first point cloud data and the second point cloud data.
9. The method of any of claims 6-8, wherein the threshold value is a difference between minimum normal retroreflection coefficients of the retroreflection target corresponding to the first observation angle and the second observation angle under the incident angle condition.
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